Recently, the frequency of signals of semiconductor devices has become increasing higher, and this makes it important to use low dielectric constant (low-k) materials as a material of the inter-layer insulation films.
As an insulation film having low dielectric constant, SiOC film, for example, is used. A number of voids are formed in the SiOC film, which realizes relatively low relative dielectric constants.
SiOC film is formed by, e.g., CVD (Chemical Vapor Deposition).
The SiOC film formed simply by CVD cannot have sufficient strength and cannot have sufficiently low relative dielectric constant either. UV cure for the purposes of improving the strength and decreasing the relative dielectric constant is made on the inter-layer insulation film of SiOC.
Related reference is as follows:    Japanese Laid-open Patent Publication No. 2005-175085.